This invention relates to insulator caps for protecting wire leads in corrosive environments.
Various systems and methods are known for protecting metal structures, such as buried pipelines, from corrosion. One such system, identified broadly as cathodic protection, mitigates electrolysis and galvanic corrosion of the pipeline by making the pipeline cathodic (negative) to the earth in which it is buried. In one system of cathodic protection, known as cathodic protection, the negative polarity on the pipeline is made possible by direct current from a rectifier which generally is energized from a commercially available 60-cycle alternating current source. The negative terminal of the rectifier is connected to the pipeline, and the positive terminal of the rectifier is connected to a ground bed reference electrode system located a substantial distance from the pipeline.
In another system of cathodic protection, a protective metal of higher potential than the structure to be protected is, in effect, utilized as the source of current. When two such dissimilar metals are placed in an electrolyte (such as soil) and connected by means of an electrical conductor, a galvanic cell is created and current flows from the metal of higher potential to the metal of lower potential. In such a system, the protective metal of higher potential becomes the anode and the protective metal of lower potential becomes the cathode. In the cathodic protection of iron and steel, magnesium is commonly used as the anode metal. In such systems the anodes are placed around or along the structure to be protected in sufficient quantity and in strategic locations to protect all parts of the structure equally.
Protective coverings and/or wrappers comprising suitable insulating and water-proofing materials, such as the various bituminous protective covering materials, are more widely used than cathodic protection systems, primarily because they are usually less expensive and more readily installed. However, for maximum protection, particularly for relatively inaccessible structures such as buried pipelines, it is quite common to employ a combination of both a protective covering system and a cathodic protection system. Employing cathodic protection in combination with protective coverings has the advantage of ensuring against imperfections or failures in the protective covering. In all types of cathodic protection, it is necessary to install various metal to metal connections between electrical conductors and the metal structure to be protected. With some metal structures, such as the pipe in buried pipelines, the protective covering material is usually placed on the pipe before and/or as it is being installed in the earth. The necessary metal to metal connections for cathodic protection are usually installed after the pipeline is in place because it is more convenient to do so. In the repair and maintenance of pipelines, such connections are always installed after the pipeline with its protective covering thereon is in place.
Installing protective and insulating covers on a substrate such as a pipeline or storage tank requires particular steps for preparing the surface. For example, the surface of a pipeline can require abrasion, cleaning and drying to improve adhesion. Further, a separate primer is generally applied to the cover and/or the pipeline which must be allowed sufficient time to dry. Such steps are often subject to minimum ambient application temperatures, which can necessitate the availability of portable heat sources. Such methods are expensive, time consuming and can lead to inconsistency of application. In pipeline applications, trench back-fill or soil movement can cause the failure of improperly established seals.